Disrupted Ionic Homeostasis in Ischemic Stroke and New Therapeutic Targets

Ginsenoside Rb1 ameliorates apical periodontitis via suppressing macrophage pyroptosis

OBJECTIVES

The objectives of current study were to investigate the role and related mechanism of Ginsenoside Rb1 (GRb1) on regulating apical periodontitis (AP) prognosis.

MATERIALS AND METHODS

Clinical specimens were used to determine the involvement of calcium overload-induced macrophage pyroptosis in periapical tissues. Next, a calcium ion-chelating agent (BAPTA-AM) was applied to detect the suppression of intracellular calcium overload in macrophage pyroptosis. Then, network pharmacology, western blot (WB) analysis, and Fluo-4 calcium assay were conducted to explore the role of GRb1 on intracellular calcium overload. To gain a better understanding of GRb1 in calcium overload-induced macrophage pyroptosis linked AP, GRb1-treated AP models were established.

RESULTS

We discovered clinically and experimentally that calcium overload-dependent macrophage pyroptosis is involved in AP pathogenesis, and reducing calcium overload greatly decreased macrophage pyroptosis in an AP cell model. Next, based on GRb1's inhibitory role in aberrant intracellular calcium accumulation, we discovered that GRb1 alleviates AP by suppressing calcium-dependent macrophage pyroptosis in both in vitro and in vivo models.

CONCLUSIONS

GRb1 is an effective therapeutic strategy to rescue the periapical tissues from inflammation due to its anti-pyroptosis function. Thus, the present study supports further investigation of GRb1 as an adjuvant therapy for AP.

TRPC Channels Activated by G Protein-Coupled Receptors Drive Ca2+ Dysregulation Leading to Secondary Brain Injury in the Mouse Model

Canonical transient receptor potential (TRPC) non-selective cation channels, particularly those assembled with TRPC3, TRPC6, and TRPC7 subunits, are coupled to Gαq-type G protein-coupled receptors for the major classes of excitatory neurotransmitters. Sustained activation of this TRPC channel-based pathophysiological signaling hub in neurons and glia likely contributes to prodigious excitotoxicity-driven secondary brain injury expansion. This was investigated in mouse models with selective Trpc gene knockout (KO). In adult cerebellar brain slices, application of glutamate and the class I metabotropic glutamate receptor agonist (S)-3,5-dihydroxyphenylglycine to Purkinje neurons expressing the GCaMP5g Ca2+ reporter demonstrated that the majority of the Ca2+ loading in the molecular layer dendritic arbors was attributable to the TRPC3 effector channels (Trpc3KO compared with wildtype (WT)). This Ca2+ dysregulation was associated with glutamate excitotoxicity causing progressive disruption of the Purkinje cell dendrites (significantly abated in a GAD67-GFP-Trpc3KO reporter brain slice model). Contribution of the Gαq-coupled TRPC channels to secondary brain injury was evaluated in a dual photothrombotic focal ischemic injury model targeting cerebellar and cerebral cortex regions, comparing day 4 post-injury in WT mice, Trpc3KO, and Trpc1/3/6/7 quadruple knockout (TrpcQKO), with immediate 2-h (primary) brain injury. Neuroprotection to secondary brain injury was afforded in both brain regions by Trpc3KO and TrpcQKO models, with the TrpcQKO showing greatest neuroprotection. These findings demonstrate the contribution of the Gαq-coupled TRPC effector mechanism to excitotoxicity-based secondary brain injury expansion, which is a primary driver for mortality and morbidity in stroke, traumatic brain injury, and epilepsy.

Pannexin1 Channel-Mediated Inflammation in Acute Ischemic Stroke

Emerging evidence suggests that inflammation mediated by the pannexin1 channel contributes significantly to acute ischemic stroke. It is believed that the pannexin1 channel is key in initiating central system inflammation during the early stages of acute ischemic stroke. Moreover, the pannexin1 channel is involved in the inflammatory cascade to maintain the inflammation levels. Specifically, the interaction of pannexin1 channels with ATP-sensitive P2X7 purinoceptors or promotion of potassium efflux mediates the activation of the NLRP3 inflammasome, triggering the release of pro-inflammatory factors such as IL-1 and IL-18, exacerbating and sustaining inflammation of brain. Also, increased release of ATP induced by cerebrovascular injury activates pannexin1 in vascular endothelial cells. This signal directs peripheral leukocytes to migrate into ischemic brain tissue, leading to an expansion of the inflammatory zone. Intervention strategies targeting pannexin1 channels may greatly alleviate inflammation after acute ischemic stroke to improve this patient population's clinical outcomes. In this review, we sought to summarize relevant studies on inflammation mediated by the pannexin1 channel in acute ischemic stroke and discussed the possibility of using brain organoid-on-a-chip technology to screen miRNAs that exclusively target the pannexin1 channel to provide new therapeutic measures for targeted regulation of pannexin1 channel to reduce inflammation in acute ischemic stroke.

Advanced Nano-Drug Delivery Systems in the Treatment of Ischemic Stroke

In recent years, the frequency of strokes has been on the rise year by year and has become the second leading cause of death around the world, which is characterized by a high mortality rate, high recurrence rate, and high disability rate. Ischemic strokes account for a large percentage of strokes. A reperfusion injury in ischemic strokes is a complex cascade of oxidative stress, neuroinflammation, immune infiltration, and mitochondrial damage. Conventional treatments are ineffective, and the presence of the blood-brain barrier (BBB) leads to inefficient drug delivery utilization, so researchers are turning their attention to nano-drug delivery systems. Functionalized nano-drug delivery systems have been widely studied and applied to the study of cerebral ischemic diseases due to their favorable biocompatibility, high efficiency, strong specificity, and specific targeting ability. In this paper, we briefly describe the pathological process of reperfusion injuries in strokes and focus on the therapeutic research progress of nano-drug delivery systems in ischemic strokes, aiming to provide certain references to understand the progress of research on nano-drug delivery systems (NDDSs).

Development of Pharmacological Strategies with Therapeutic Potential in Ischemic Stroke

Acute ischemic stroke constitutes a health challenge with great social impact due to its high incidence, with the social dependency that it generates being an important source of inequality. The lack of treatments serving as effective neuroprotective therapies beyond thrombolysis and thrombectomy is presented as a need. With this goal in mind, our research group's collaborative studies into cerebral ischemia and subsequent reperfusion concluded that there is a need to develop compounds with antioxidant and radical scavenger features. In this review, we summarize the path taken toward the identification of lead compounds as potential candidates for the treatment of acute ischemic stroke. Evaluations of the antioxidant capacity, neuroprotection of primary neuronal cultures and in vivo experimental models of cerebral ischemia, including neurological deficit score assessments, are conducted to characterize the biological efficacy of the various neuroprotective compounds developed. Moreover, the initial results in preclinical development, including dose-response studies, the therapeutic window, the long-term neuroprotective effect and in vivo antioxidant evaluation, are reported. The results prompt these compounds for clinical trials and are encouraging regarding new drug developments aimed at a successful therapy for ischemic stroke.

Hyperglycemia exacerbates ischemic stroke not through increased generation of hydrogen peroxide

Diabetes is one of the significant risk factors for ischemic stroke. Hyperglycemia exacerbates the pathogenesis of stroke, leading to more extensive cerebral damage and, as a result, to more severe consequences. However, the mechanism whereby the hyperglycemic status in diabetes affects biochemical processes during the development of ischemic injury is still not fully understood. In the present work, we record for the first time the real-time dynamics of H2O2 in the matrix of neuronal mitochondria in vitro in culture and in vivo in the brain tissues of rats during development of ischemic stroke under conditions of hyperglycemia and normal glucose levels. To accomplish this, we used a highly sensitive HyPer7 biosensor and a fiber-optic interface technology. We demonstrated that a high glycemic status does not affect the generation of H2O2 in the tissues of the ischemic core, while significantly exacerbating the consequences of pathogenesis. For the first time using Raman microspectroscopy approach, we have shown how a sharp increase in the blood glucose level increases the relative amount of reduced cytochromes in the mitochondrial electron transport chain in neurons under normal conditions in awake mice.

The Pathological Mechanism of Neuronal Autophagy-Lysosome Dysfunction After Ischemic Stroke

The abnormal initiation of autophagy flux in neurons after ischemic stroke caused dysfunction of autophagy-lysosome, which not only led to autophagy flux blockage, but also resulted in autophagic death of neurons. However, the pathological mechanism of neuronal autophagy-lysosome dysfunction did not form a unified viewpoint until now. In this review, taking the autophagy lysosomal dysfunction of neurons as a starting point, we summarized the molecular mechanisms that led to neuronal autophagy lysosomal dysfunction after ischemic stroke, which would provide theoretical basis for the clinical treatment of ischemic stroke.

Multinuclear MRI Reveals Early Efficacy of Stem Cell Therapy in Stroke

Compromised adult human mesenchymal stem cells (hMSC) can impair cell therapy efficacy and further reverse ischemic recovery. However, in vitro assays require extended passage to characterize cells, limiting rapid assessment for therapeutic potency. Multinuclear magnetic resonance imaging and spectroscopy (MRI/S) provides near real-time feedback on disease progression and tissue recovery. Applied to ischemic stroke, 23Na MRI evaluates treatment efficacy within 24 h after middle cerebral artery occlusion, showing recovery of sodium homeostasis and lesion reduction in specimens treated with hMSC while 1H MRS identifies reduction in lactate levels. This combined metric was confirmed by evaluating treatment groups receiving healthy or compromised hMSC versus vehicle (sham saline injection) over 21 days. Behavioral tests to assess functional recovery and cell analysis for immunomodulatory and macrophage activity to detect hMSC potency confirm MR findings. Clinically, these MR metrics may prove critical to early evaluations of therapeutic efficacy and overall stroke recovery.

Animal toxins: As an alternative therapeutic target following ischemic stroke condition

Globally, Ischemic stroke (IS) has become the second leading cause of mortality and chronic disability. The process of IS has triggered by the blockages of blood vessels to form clots in the brain which initiates multiple interactions with the key signaling pathways, counting excitotoxicity, acidosis, ionic imbalance, inflammation, oxidative stress, and neuronal dysfunction of cells, and ultimately cells going under apoptosis. Currently, FDA has approved only tissue plasminogen activator therapy, which is effective against IS with few limitations. However, the mechanism of excitotoxicity and acidosis has spurred the investigation of a potential candidate for IS therapy. Acid-sensing ion channels (ASICs) and Voltage-gated Ca²⁺ channels (VDCCs) get activated and disturb the brain's normal physiology. Animal toxins are novel inhibitors of ASICs and VDCCs channels and have provided neuroprotective insights into the pathophysiology of IS. This review will discuss the potential directions of translational ASICs and VDCCs inhibitors research for clinical therapies.

Modeling the heterogeneity of sodium and calcium homeostasis between cortical and hippocampal astrocytes and its impact on bioenergetics

Emerging evidence indicates that neuronal activity-evoked changes in sodium concentration in astrocytes Na _a represent a special form of excitability, which is tightly linked to all other major ions in the astrocyte and extracellular space, as well as to bioenergetics, neurotransmitter uptake, and neurovascular coupling. Recently, one of us reported that Na _a transients in the neocortex have a significantly higher amplitude than those in the hippocampus. Based on the extensive data from that study, here we develop a detailed biophysical model to further understand the origin of this heterogeneity and how it affects bioenergetics in the astrocytes. In addition to closely fitting the observed experimental Na _a changes under different conditions, our model shows that the heterogeneity in Na _a signaling leads to substantial differences in the dynamics of astrocytic Ca²⁺ signals in the two brain regions, and leaves cortical astrocytes more susceptible to Na⁺ and Ca²⁺ overload under metabolic stress. The model also predicts that activity-evoked Na _a transients result in significantly larger ATP consumption in cortical astrocytes than in the hippocampus. The difference in ATP consumption is mainly due to the different expression levels of NMDA receptors in the two regions. We confirm predictions from our model experimentally by fluorescence-based measurement of glutamate-induced changes in ATP levels in neocortical and hippocampal astrocytes in the absence and presence of the NMDA receptor's antagonist (2R)-amino-5-phosphonovaleric acid.

Autophagy and Apoptosis in Acute Brain Injuries: From Mechanism to Treatment

Significance: Autophagy and apoptosis are two important cellular mechanisms behind brain injuries, which are severe clinical situations with increasing incidences worldwide. To search for more and better treatments for brain injuries, it is essential to deepen the understanding of autophagy, apoptosis, and their interactions in brain injuries. This article first analyzes how autophagy and apoptosis participate in the pathogenetic processes of brain injuries respectively and mutually, then summarizes some promising treatments targeting autophagy and apoptosis to show the potential clinical applications in personalized medicine and precision medicine in the future. Recent Advances: Most current studies suggest that apoptosis is detrimental to brain recovery. Several studies indicate that autophagy can cause unnecessary death of neurons after brain injuries, while others show that autophagy is beneficial for acute brain injuries (ABIs) by facilitating the removal of damaged proteins and organelles. Whether autophagy is beneficial or detrimental in ABIs depends on many factors, and the results from different research groups are diverse or even controversial, making this topic more appealing to be explored further. Critical Issues: Neuronal autophagy and apoptosis are two primary pathological processes in ABIs. How they interact with each other and how their regulations affect the outcome and prognosis of brain injuries remain uncertain, making these answers more critical. Future Directions: Insights into the interplay between autophagy and apoptosis and the accurate regulations of their balance in ABIs may promote personalized and precise treatments in the field of brain injuries. Antioxid. Redox Signal. 38, 234-257.

The role of NLRP3 inflammasome-mediated pyroptosis in ischemic stroke and the intervention of traditional Chinese medicine

Ischemic stroke (IS) is the second leading cause of death and disability in the world. Pyroptosis, a form of programmed cell death initiated by caspases, participates in the occurrence and development of IS. Because it can increase cell membrane permeability, mediate the release of inflammatory factors, and aggravate inflammation, inhibiting this process can significantly reduce the pathological injury of IS. The nucleotide binding oligomerization domain-like receptor family pyrin domain protein 3 (NLRP3) is a multiprotein complex whose activation is the core link of pyroptosis. In recent years, studies have reported that traditional Chinese medicine (TCM) could regulate pyroptosis mediated by NLRP3 inflammasome through multi-channel and multi-target networks and thus exert the effect against IS. This article reviews 107 papers published in recent years in PubMed, Chinese National Knowledge Infrastructure (CNKI), and WanFang Data in recent years. It has found that the activation factors of NLRP3 inflammasome include ROS, mitochondrial dysfunction, K⁺, Ca²⁺, lysosome rupture, and trans-Golgi breakdown. TLR4/NF-κB/NLRP3, ROS/TXNIP/NLRP3, AMPK/Nrf2/NLRP3, DRP1/NLRP3, TAK1/JNK/NLRP3 signaling pathways regulate the initiation and assembly of the NLRP3 inflammasome, subsequently induce pyroptosis, affecting the occurrence and development of IS. TCM can affect the above signaling pathways and regulate the pyroptosis mediated by NLRP3 inflammasome, so as to play a protective role against IS, which provides a new entry point for discussing the pathological mechanism of IS and a theoretical basis for developing TCM treasure house.

New insights in ferroptosis: Potential therapeutic targets for the treatment of ischemic stroke

Stroke is a common disease in clinical practice, which seriously endangers people's physical and mental health. The neurovascular unit (NVU) plays a key role in the occurrence and development of ischemic stroke. Different from other classical types of cell death such as apoptosis, necrosis, autophagy, and pyroptosis, ferroptosis is an iron-dependent lipid peroxidation-driven new form of cell death. Interestingly, the function of NVU and stroke development can be regulated by activating or inhibiting ferroptosis. This review systematically describes the NVU in ischemic stroke, provides a comprehensive overview of the regulatory mechanisms and key regulators of ferroptosis, and uncovers the role of ferroptosis in the NVU and the progression of ischemic stroke. We further discuss the latest progress in the intervention of ferroptosis as a therapeutic target for ischemic stroke and summarize the research progress and regulatory mechanism of ferroptosis inhibitors on stroke. In conclusion, ferroptosis, as a new form of cell death, plays a key role in ischemic stroke and is expected to become a new therapeutic target for this disease.

In vivo evaluation and molecular docking studies of Schinus molle L. fruit extract protective effect against isoproterenol-induced infarction in rats

The aim of the current study was to assess the potential cardiopreventive effect of the methanolic extract of S. molle L. (MESM) on isoproterenol-induced infarction in rats. The biomolecules content was evaluated using HPLC-DAD-ESI-QTOF-MS/MS analysis. On the 29th and 30th days, two successive injections of isoproterenol (ISO) were given to Wistar rats to provoke myocardial infarction following pretreatment with either MESM (60 mg/kg b.w) or Pidogrel (Pid; 2 mg/kg b.w.). A total of sixteen phenolics were identified with masazino-flavanone as the most prevalent compound (1726.12 µg/g dm). Results showed that MESM offered cardioprevention by normalizing the ST segment and reducing the elevated cardiac risk parameters. The altered lipid biomarkers together with the plasma ionic levels were improved. Additionally, MESM inhibited the cardiac oxidative stress generated by ISO injection though enhancing antioxidant enzymes (GSH, CAT, SOD and GPX) which reduced lipid peroxidation and protein oxidation. MESM reduced myocardial apoptosis by significantly repressing mRNA expressions of Caspase-3 and Bax, with an upregulated Bcl-2 expression. Moreover, MESM reduced DNA fragmentation as well as the infarct size observed by TTC staining. In addition, MESM exhibited an antifibrotic effect by downregulating TGF-1β expression and reducing collagen deposition in myocardial tissue, as confirmed by Trichrom Masson analysis. The histopathological findings revealed less muscle separation and fewer inflammatory cells in the ISO + MESM-treated rats. Results of the docking simulation indicated that catechin in MESM was inhibitory mainly due to hydrogen bonding interactions with PDI, ACE and TGF-β1 proteins which could highlight the antithrombotic and antifibrotic capacity of MESM.

Ion Channels and Transporters as Therapeutic Agents: From Biomolecules to Supramolecular Medicinal Chemistry

Ion channels and transporters typically consist of biomolecules that play key roles in a large variety of physiological and pathological processes. Traditional therapies include many ion-channel blockers, and some activators, although the exact biochemical pathways and mechanisms that regulate ion homeostasis are yet to be fully elucidated. An emerging area of research with great innovative potential in biomedicine pertains the design and development of synthetic ion channels and transporters, which may provide unexplored therapeutic opportunities. However, most studies in this challenging and multidisciplinary area are still at a fundamental level. In this review, we discuss the progress that has been made over the last five years on ion channels and transporters, touching upon biomolecules and synthetic supramolecules that are relevant to biological use. We conclude with the identification of therapeutic opportunities for future exploration.

Neuroinflammation and COVID-19 Ischemic Stroke Recovery—Evolving Evidence for the Mediating Roles of the ACE2/Angiotensin-(1–7)/Mas Receptor Axis and NLRP3 Inflammasome

Cerebrovascular events, notably acute ischemic strokes (AIS), have been reported in the setting of novel coronavirus disease (COVID-19) infection. Commonly regarded as cryptogenic, to date, the etiology is thought to be multifactorial and remains obscure; it is linked either to a direct viral invasion or to an indirect virus-induced prothrombotic state, with or without the presence of conventional cerebrovascular risk factors. In addition, patients are at a greater risk of developing long-term negative sequelae, i.e., long-COVID-related neurological problems, when compared to non-COVID-19 stroke patients. Central to the underlying neurobiology of stroke recovery in the context of COVID-19 infection is reduced angiotensin-converting enzyme 2 (ACE2) expression, which is known to lead to thrombo-inflammation and ACE2/angiotensin-(1–7)/mitochondrial assembly receptor (MasR) (ACE2/Ang-(1-7)/MasR) axis inhibition. Moreover, after AIS, the activated nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome may heighten the production of numerous proinflammatory cytokines, mediating neuro-glial cell dysfunction, ultimately leading to nerve-cell death. Therefore, potential neuroprotective therapies targeting the molecular mechanisms of the aforementioned mediators may help to inform rehabilitation strategies to improve brain reorganization (i.e., neuro-gliogenesis and synaptogenesis) and secondary prevention among AIS patients with or without COVID-19. Therefore, this narrative review aims to evaluate the mediating role of the ACE2/Ang- (1-7)/MasR axis and NLRP3 inflammasome in COVID-19-mediated AIS, as well as the prospects of these neuroinflammation mediators for brain repair and in secondary prevention strategies against AIS in stroke rehabilitation.

Suppressing Effect of Na+/Ca2+ Exchanger (NCX) Inhibitors on the Growth of Melanoma Cells

The role of calcium ion (Ca²⁺) signaling in tumorigenicity has received increasing attention in melanoma research. Previous Ca²⁺ signaling studies focused on Ca²⁺ entry routes, but rarely explored the role of Ca²⁺ extrusion. Functioning of the Na⁺/Ca²⁺ exchanger (NCX) on the plasma membrane is the major way of Ca²⁺ extrusion, but very few associations between NCX and melanoma have been reported. Here, we explored whether pharmacological modulation of the NCX could suppress melanoma and promise new therapeutic strategies. Methods included cell viability assay, Ca²⁺ imaging, immunoblotting, and cell death analysis. The NCX inhibitors SN-6 and YM-244769 were used to selectively block reverse operation of the NCX. Bepridil, KB-R7943, and CB-DMB blocked either reverse or forward NCX operation. We found that blocking the reverse NCX with SN-6 or YM-244769 (5–100 μM) did not affect melanoma cells or increase cytosolic Ca²⁺. Bepridil, KB-R7943, and CB-DMB all significantly suppressed melanoma cells with IC₅₀ values of 3–20 μM. Bepridil and KB-R7943 elevated intracellular Ca²⁺ level of melanoma. Bepridil-induced melanoma cell death came from cell cycle arrest and enhanced apoptosis, which were all attenuated by the Ca²⁺ chelator BAPTA-AM. As compared with melanoma, normal melanocytes had lower NCX1 expression and were less sensitive to the cytotoxicity of bepridil. In conclusion, blockade of the forward but not the reverse NCX leads to Ca²⁺-related cell death in melanoma and the NCX is a potential drug target for cancer therapy.

Evaluation and Prediction of Post-stroke Cerebral Edema Based on Neuroimaging

Cerebral edema is a common complication of acute ischemic stroke that leads to poorer functional outcomes and substantially increases the mortality rate. Given that its negative effects can be reduced by more intensive monitoring and evidence-based interventions, the early identification of patients with a high risk of severe edema is crucial. Neuroimaging is essential for the assessment and prediction of edema. Simple markers, such as midline shift and hypodensity volume on computed tomography, have been used to evaluate edema in clinical trials; however, advanced techniques can be applied to examine the underlying mechanisms. In this study, we aimed to review current imaging tools in the assessment and prediction of cerebral edema to provide guidance for using these methods in clinical practice.

Pharmacological Modulation and (Patho)Physiological Roles of TRPM4 Channel-Part 2: TRPM4 in Health and Disease

Transient receptor potential melastatin 4 (TRPM4) is a unique member of the TRPM protein family and, similarly to TRPM5, is Ca²⁺ sensitive and permeable for monovalent but not divalent cations. It is widely expressed in many organs and is involved in several functions; it regulates membrane potential and Ca²⁺ homeostasis in both excitable and non-excitable cells. This part of the review discusses the currently available knowledge about the physiological and pathophysiological roles of TRPM4 in various tissues. These include the physiological functions of TRPM4 in the cells of the Langerhans islets of the pancreas, in various immune functions, in the regulation of vascular tone, in respiratory and other neuronal activities, in chemosensation, and in renal and cardiac physiology. TRPM4 contributes to pathological conditions such as overactive bladder, endothelial dysfunction, various types of malignant diseases and central nervous system conditions including stroke and injuries as well as in cardiac conditions such as arrhythmias, hypertrophy, and ischemia-reperfusion injuries. TRPM4 claims more and more attention and is likely to be the topic of research in the future.

Anti-embolic and anti-oxidative effects of a novel (E)-4-amino-N'-(1-(7-hydroxy-2-oxo-2H-chromen-3-yl) ethylidene) benzohydrazide against isoproterenol and vitamin-K induced ischemic stroke

This study aimed to evaluate the cerebroprotective potential of a novel synthetic coumarin, (E)-4-amino-N'-(1-(7-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene) benzohydrazide noted (HC) against a pharmaceutically induced ischemic stroke in experimental male Wistar rats. Animals were randomly allocated into four groups: control, Stroke, Stroke + Ace (acenocoumarol) and Stroke + HC-treated group for 7 days. Our results showed that stroke group evidenced atrial flutter, significant cardiac hypertrophy (+23%) and increase in plasma level of troponin-T, with disturbance in plasma ionic levels and rise in fibrinogen rate and oxidative damages in heart and brain. Moreover, the histological findings revealed myocardium necrosis, cardiac cavity thrombi and brain injury as compared to normal rats. However, HC-treatment significantly prevents the embolic process, improves cerebral damages and mitigates the oxidative stress markers in stroke rats. Overall, HC is endowed with a thrombolytic potential against MI and stroke in such severe conditions through an anti-vit K (AVK) mechanism.

Hemorrhagic Stroke Induces a Time-Dependent Upregulation of miR-150-5p and miR-181b-5p in the Bloodstream

To date, the only effective pharmacological treatment for ischemic stroke is limited to the clinical use of recombinant tissue plasminogen activator (rtPA), although endovascular therapy has also emerged as an effective treatment for acute ischemic stroke. Unfortunately, the benefit of this treatment is limited to a 4.5-h time window. Most importantly, the use of rtPA is contraindicated in the case of hemorrhagic stroke. Therefore, the identification of a reliable biomarker to distinguish hemorrhagic from ischemic stroke could provide several advantages, including an earlier diagnosis, a better treatment, and a faster decision on ruling out hemorrhage so that tPA may be administered earlier. microRNAs (miRNAs) are stable non-coding RNAs crucially involved in the downregulation of gene expression via mRNA cleavage or translational repression. In the present paper, taking advantage of three preclinical animal models of stroke, we compared the miRNA blood levels of animals subjected to permanent or transient middle cerebral artery occlusion (MCAO) or to collagenase-induced hemorrhagic stroke. Preliminarily, we examined the rat miRNome in the brain tissue of ischemic and sham-operated rats; then, we selected those miRNAs whose expression was significantly modulated after stroke to create a list of miRNAs potentially involved in stroke damage. These selected miRNAs were then evaluated at different time intervals in the blood of rats subjected to permanent or transient focal ischemia or to hemorrhagic stroke. We found that four miRNAs-miR-16-5p, miR-101a-3p, miR-218-5p, and miR-27b-3p-were significantly upregulated in the plasma of rats 3 h after permanent MCAO, whereas four other different miRNAs-miR-150-5p, let-7b-5p, let-7c-5p, and miR-181b-5p-were selectively upregulated by collagenase-induced hemorrhagic stroke. Collectively, our study identified some selective miRNAs expressed in the plasma of hemorrhagic rats and pointed out the importance of a precise time point measurement to render more reliable the use of miRNAs as stroke biomarkers.

Therapeutic time windows of compounds against NMDA receptors signaling pathways for ischemic stroke

Much evidence has proved that excitotoxicity induced by excessive release of glutamate contributes largely to damage caused by ischemia. In view of the key role played by NMDA receptors in mediating excitotoxicity, compounds against NMDA receptors signaling pathways have become the most promising type of anti-stroke candidate compounds. However, the limited therapeutic time window for neuroprotection is a key factor preventing NMDA receptor-related compounds from showing efficacy in all clinical trials for ischemic stroke. In this perspective, the determination of therapeutic time windows of these kinds of compounds is useful in ensuring a therapeutic effect and accelerating clinical application. This mini-review discussed the therapeutic time windows of compounds against NMDA receptors signaling pathways, described related influence factors and the status of clinical studies. The purpose of this review is to look for compounds with wide therapeutic time windows and better clinical application prospect.

Molecular Mechanisms of Neuroimmune Crosstalk in the Pathogenesis of Stroke

Stroke disrupts the homeostatic balance within the brain and is associated with a significant accumulation of necrotic cellular debris, fluid, and peripheral immune cells in the central nervous system (CNS). Additionally, cells, antigens, and other factors exit the brain into the periphery via damaged blood–brain barrier cells, glymphatic transport mechanisms, and lymphatic vessels, which dramatically influence the systemic immune response and lead to complex neuroimmune communication. As a result, the immunological response after stroke is a highly dynamic event that involves communication between multiple organ systems and cell types, with significant consequences on not only the initial stroke tissue injury but long-term recovery in the CNS. In this review, we discuss the complex immunological and physiological interactions that occur after stroke with a focus on how the peripheral immune system and CNS communicate to regulate post-stroke brain homeostasis. First, we discuss the post-stroke immune cascade across different contexts as well as homeostatic regulation within the brain. Then, we focus on the lymphatic vessels surrounding the brain and their ability to coordinate both immune response and fluid homeostasis within the brain after stroke. Finally, we discuss how therapeutic manipulation of peripheral systems may provide new mechanisms to treat stroke injury.

Relevant mediators involved in and therapies targeting the inflammatory response induced by activation of the NLRP3 inflammasome in ischemic stroke

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is a member of the NLR family of inherent immune cell sensors. The NLRP3 inflammasome can detect tissue damage and pathogen invasion through innate immune cell sensor components commonly known as pattern recognition receptors (PRRs). PRRs promote activation of nuclear factor kappa B (NF-κB) pathways and the mitogen-activated protein kinase (MAPK) pathway, thus increasing the transcription of genes encoding proteins related to the NLRP3 inflammasome. The NLRP3 inflammasome is a complex with multiple components, including an NAIP, CIITA, HET-E, and TP1 (NACHT) domain; apoptosis-associated speck-like protein containing a CARD (ASC); and a leucine-rich repeat (LRR) domain. After ischemic stroke, the NLRP3 inflammasome can produce numerous proinflammatory cytokines, mediating nerve cell dysfunction and brain edema and ultimately leading to nerve cell death once activated. Ischemic stroke is a disease with high rates of mortality and disability worldwide and is being observed in increasingly younger populations. To date, there are no clearly effective therapeutic strategies for the clinical treatment of ischemic stroke. Understanding the NLRP3 inflammasome may provide novel ideas and approaches because targeting of upstream and downstream molecules in the NLRP3 pathway shows promise for ischemic stroke therapy. In this manuscript, we summarize the existing evidence regarding the composition and activation of the NLRP3 inflammasome, the molecules involved in inflammatory pathways, and corresponding drugs or molecules that exert effects after cerebral ischemia. This evidence may provide possible targets or new strategies for ischemic stroke therapy.

Zebrafish as a Model for In-Depth Mechanistic Study for Stroke

Stroke is one of the world's leading causes of death and disability, posing enormous burden to the society. However, the pathogenesis and mechanisms that underlie brain injury and brain repair remain largely unknown. There's an unmet need of in-depth mechanistic research in this field. Zebrafish (Danio rerio) is a powerful tool in brain science research mainly due to its small size and transparent body, high genome synteny with human, and similar nervous system structures. It can be used to establish both hemorrhagic and ischemic stroke models easily and effectively through different ways. After the establishment of stroke model, research methods including behavioral test, in vivo imaging, and drug screening are available to explore mechanisms that underlie the brain injury and brain repair after stroke. This review focuses on the advantages and the feasibility of zebrafish stroke model, and will also introduce the key methods available for stroke studies in zebrafish, which may drive future mechanistic studies in the pursuit of discovering novel therapeutic targets for stroke patients.

Role of Calcium Homeostasis in Ischemic Stroke: A Review

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Stroke is the second most common cause of death worldwide. It occurs due to the insufficient supply of oxygen-rich blood to the brain. It is a complex disease with multiple associated risk factors including smoking, alcoholism, age, sex, ethnicity, etc. Calcium ions are known to play a vital role in cell death pathways, which is a ubiquitous intracellular messenger during and immediately after an ischemic period. Disruption in normal calcium hemostasis is known to be a major initiator and activator of the ischemic cell death pathway. Under Ischemic stroke conditions, glutamate is released from the neurons and glia which further activates the N-methyl-D-aspartate (NMDA) receptor and triggers the rapid translocation of Ca2+ from extracellular to intracellular spaces in cerebral tissues and vice versa. Various studies indicated that Ca2+ could have harmful effects on neurons under acute ischemic conditions. Mitochondrial dysfunction also contributes to delayed neuronal death, and it was established decades ago that massive calcium accumulation triggers mitochondrial damage. Elevated Ca2+ levels cause mitochondria to swell and release their contents. As a result oxidative stress and mitochondrial calcium accumulation activate mitochondrial permeability transition and lead to depolarization-coupled production of reactive oxygen species. This association between calcium levels and mitochondrial death suggests that elevated calcium levels might have a role in the neurological outcome in ischemic stroke. Previous studies have also reported that elevated Ca2+ levels play a role in the determination of infarct size, outcome, and recurrence of ischemic stroke. The current review has been compiled to understand the multidimensional role of altered Ca2+ levels in the initiation and alteration of neuronal death after ischemic attack. The underlying mechanisms understood to date have also been discussed.

Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment in Acute Ischemic Stroke

Hemorrhagic transformation (HT) is a common complication after thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in ischemic stroke. In this article, recent research progress of HT in vivo and in vitro studies was reviewed. We have discussed new potential mechanisms and possible experimental models of HT development, as well as possible biomarkers and treatment methods. Meanwhile, we compared and analyzed rodent models, large animal models and in vitro BBB models of HT, and the limitations of these models were discussed. The molecular mechanism of HT was investigated in terms of BBB disruption, rt-PA neurotoxicity and the effect of neuroinflammation, matrix metalloproteinases, reactive oxygen species. The clinical features to predict HT were represented including blood biomarkers and clinical factors. Recent progress in neuroprotective strategies to improve HT after stroke treated with rt-PA is outlined. Further efforts need to be made to reduce the risk of HT after rt-PA therapy and improve the clinical prognosis of patients with ischemic stroke.

Treadmill exercise attenuates cerebral ischaemic injury in rats by protecting mitochondrial function via enhancement of caveolin-1

AIMS

Exercise training has a neuroprotective effect against ischaemic injury, but the underlying mechanism is not completely clear. This study explored the potential mechanisms underlying the protective effects of treadmill training and caveolin-1 regulation against mitochondrial dysfunction in cerebral ischaemic injury.

MAIN METHODS

After middle cerebral artery occlusion (MCAO) surgery, rats were subjected to treadmill training and received daidzein injections and combined therapy. A series of analyses, including neurological function scoring; body weight measurement; Nissl, haematoxylin and eosin staining; cerebral infarction volume assessment; mitochondrial morphology examination; caveolin-1, cytoplasmic and mitochondrial cytochrome C (CytC), and translocase of outer membrane 20 (TOM20) expression analysis; apoptosis index analysis; and transmission electron microscopy were conducted.

KEY FINDINGS

Treadmill training increased caveolin-1 expression, reduced neurobehavioral scores and cerebral infarction volumes, improved tissue morphology, reduced neuronal loss, inhibited mitochondrial outer membrane permeabilization (MOMP) through the caveolin-1 pathway, prevented excessive Cyt-C release from mitochondria, and reduced the degrees of apoptosis and mitochondrial damage. In addition, treadmill training increased the expression of TOM20 through the caveolin-1 pathway and maintained import signal function, thereby protecting mitochondrial integrity.

SIGNIFICANCE

Treadmill exercise protected mitochondrial integrity and inhibited the endogenous mitochondrial apoptosis pathway. The damage of cerebral ischaemia was alleviated in rats through enhancement of caveolin-1 by treadmill exercise.

Comparison of Anti-oncotic Effect of TRPM4 Blocking Antibody in Neuron, Astrocyte and Vascular Endothelial Cell Under Hypoxia

In stroke and other neurological diseases, Transient Receptor Potential Melastatin 4 (TRPM4) has been reported to cause oncotic cell death which is due to an excessive influx of sodium ions. Following stroke, hypoxia condition activates TRPM4 channel, and the sodium influx via TRPM4 is further enhanced by an increased TRPM4 expression. However, the effect of TRPM4 inhibition on oncotic cell death, particularly during the acute stage, remains largely unknown. Recently, we have developed a polyclonal antibody M4P that specifically inhibits TRPM4 channel. M4P blocks the channel via binding to a region close to the channel pore from extracellular space. Using M4P, we evaluated the acute effect of blocking TRPM4 in neurons, astrocytes, and vascular endothelial cells. In a rat stroke model, M4P co-localized with neuronal marker NeuN and endothelial marker vWF, whereas few GFAP positive astrocytes were stained by M4P in the ipsilateral hemisphere. When ATP was acutely depleted in cultured cortical neurons and microvascular endothelial cells, cell swelling was induced. Application of M4P significantly blocked TRPM4 current and attenuated oncosis. TUNEL assay, PI staining and western blot on cleaved Caspase-3 revealed that M4P could ameliorate apoptosis after 24 h hypoxia exposure. In contrast, acute ATP depletion in cultured astrocytes failed to demonstrate an increase of cell volume, and application of M4P or control IgG had no effect on cell volume change. When TRPM4 was overexpressed in astrocytes, acute ATP depletion successfully induced oncosis which could be suppressed by M4P treatment. Our results demonstrate that comparing to astrocytes, neurons, and vascular endothelial cells are more vulnerable to hypoxic injury. During the acute stage of stroke, blocking TRPM4 channel could protect neurons and vascular endothelial cells from oncotic cell death.

The Role of NLRP3 Inflammasome in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) represents an important problem of global health. The damage related to TBI is first due to the direct injury and then to a secondary phase in which neuroinflammation plays a key role. NLRP3 inflammasome is a component of the innate immune response and different diseases, such as neurodegenerative diseases, are characterized by NLRP3 activation. This review aims to describe NLRP3 inflammasome and the consequences related to its activation following TBI. NLRP3, caspase-1, IL-1β, and IL-18 are significantly upregulated after TBI, therefore, the use of nonspecific, but mostly specific NLRP3 inhibitors is useful to ameliorate the damage post-TBI characterized by neuroinflammation. Moreover, NLRP3 and the molecules associated with its activation may be considered as biomarkers and predictive factors for other neurodegenerative diseases consequent to TBI. Complications such as continuous stimuli or viral infections, such as the SARS-CoV-2 infection, may worsen the prognosis of TBI, altering the immune response and increasing the neuroinflammatory processes related to NLRP3, whose activation occurs both in TBI and in SARS-CoV-2 infection. This review points out the role of NLRP3 in TBI and highlights the hypothesis that NLRP3 may be considered as a potential therapeutic target for the management of neuroinflammation in TBI.

The Role of Transient Receptor Potential Channels in Blood-Brain Barrier Dysfunction after Ischemic Stroke

Stroke is the leading cause of long-term disability, demanding an ever-increasing need to find treatment. Transient receptor potential (TRP) channels are nonselective Ca²⁺-permeable channels, among which TRPC, TRPM, and TRPV are widely expressed in the brain. Dysfunction of the blood brain barrier (BBB) is a core feature of stroke and is associated with severity of injury. As studies have shown, TRP channels influence various neuronal functions by regulating the BBB. Here, we briefly review the role of TRP channel in the BBB dysfunction after stroke, and explore the therapeutic potential of TRP-targeted therapy.

Transient Receptor Potential Melastatin 2 (TRPM2) Inhibition by Antioxidant, N-Acetyl-l-Cysteine, Reduces Global Cerebral Ischemia-Induced Neuronal Death

A variety of pathogenic mechanisms, such as cytoplasmic calcium/zinc influx, reactive oxygen species production, and ionic imbalance, have been suggested to play a role in cerebral ischemia induced neurodegeneration. During the ischemic state that occurs after stroke or heart attack, it is observed that vesicular zinc can be released into the synaptic cleft, and then translocated into the cytoplasm via various cation channels. Transient receptor potential melastatin 2 (TRPM2) is highly distributed in the central nervous system and has high sensitivity to oxidative damage. Several previous studies have shown that TRPM2 channel activation contributes to neuroinflammation and neurodegeneration cascades. Therefore, we examined whether anti-oxidant treatment, such as with N-acetyl-l-cysteine (NAC), provides neuroprotection via regulation of TRPM2, following global cerebral ischemia (GCI). Experimental animals were then immediately injected with NAC (150 mg/kg/day) for 3 and 7 days, before sacrifice. We demonstrated that NAC administration reduced activation of GCI-induced neuronal death cascades, such as lipid peroxidation, microglia and astroglia activation, free zinc accumulation, and TRPM2 over-activation. Therefore, modulation of the TRPM2 channel can be a potential therapeutic target to prevent ischemia-induced neuronal death.

Predictors of urinary tract infection in acute stroke patients: A cohort study

Patients with stroke have a high risk of infection which may be predicted by age, procalcitonin, interleukin-6, C-reactive protein, National Institute of Health stroke scale (NHSS) score, diabetes, etc. These prediction methods can reduce unfavourable outcome by preventing the occurrence of infection.We aim to identify early predictors for urinary tract infection in patients after stroke.In 186 collected acute stroke patients, we divided them into urinary tract infection group, other infection type groups, and non-infected group. Data were recorded at admission. Independent risk factors and infection prediction model were determined using Logistic regression analyses. Likelihood ratio test was used to detect the prediction effect of the model. Receiver operating characteristic curve and the corresponding area under the curve were used to measure the predictive accuracy of indicators for urinary tract infection.Of the 186 subjects, there were 35 cases of urinary tract infection. Elevated interleukin-6, higher NIHSS, and decreased hemoglobin may be used to predict urinary tract infection. And the predictive model for urinary tract infection (including sex, NIHSS, interleukin-6, and hemoglobin) have the best predictive effect.This study is the first to discover that decreased hemoglobin at admission may predict urinary tract infection. The prediction model shows the best accuracy.

iTRAQ-based proteomic analysis after mesenchymal stem cell line transplantation for ischemic stroke

Transplantation with mesenchymal stem cells (MSCs) has been reported to promote functional recovery in animal models of ischemic stroke. However, the molecular mechanisms underlying the therapeutic effects of MSC transplantation have been only partially elucidated. The purpose of this study was to comprehensively identify changes in brain proteins in rats treated with MSCs for ischemic stroke, and to explore the multi-target mechanisms of MSCs using a proteomics-based strategy. Twenty-eight proteins were found to be differentially expressed following B10 MSC transplantation in adult male Wistar rats, as assessed using isobaric tagging for relative and absolute protein quantification (iTRAQ). Subsequent bioinformatic analysis revealed that these proteins were mainly associated with energy metabolism, glutamate excitotoxicity, oxidative stress, and brain structural and functional plasticity. Immunohistochemical staining revealed decreased expression of EAAT1 in the phosphate-buffered saline group as opposed to normal levels in the B10 transplantation group. Furthermore, ATP levels were also significantly higher in the B10 transplantation group, thus supporting the iTRAQ results. Our results suggest that the therapeutic effects of B10 transplantation might arise from the modulation of the acute ischemic cascade via multiple molecular pathways. Thus, our findings provide valuable clues to elucidate the mechanisms underlying the therapeutic effects of MSC transplantation in ischemic stroke.

Resveratrol reduces cerebral edema through inhibition of de novo SUR1 expression induced after focal ischemia

Cerebral edema is a clinical problem that frequently follows ischemic infarcts. Sulfonylurea receptor 1 (SUR1) is an inducible protein that can form a heteromultimeric complex with aquaporin 4 (AQP4) that mediate the ion/water transport involved in brain tissue swelling. Transcription of the Abcc8 gene coding for SUR1 depends on the activity of transcriptional factor SP1, which is modulated by the cellular redox environment. Since oxidative stress is implicated in the induced neuronal damage in ischemia and edema formation, the present study aimed to evaluate if the antioxidant resveratrol (RSV) prevents the damage by reducing the de novo expression of SUR1 in the ischemic brain. Male Wistar rats were subjected to 2 h of middle cerebral artery occlusion followed by different times of reperfusion. RSV (1.9 mg/kg; i.v.) was administered at the onset of reperfusion. Brain damage and edema formation were recognized by neurological evaluation, time of survival, TTC (2,3,5-Triphenyltetrazolium chloride) staining, Evans blue extravasation, and water content. RSV mechanism of action was studied by SP1 binding activity measured through the Electrophoretic Mobility Shift Assay, and Abcc8 and Aqp4 gene expression evaluated by qPCR, immunofluorescence, and Western blot. We found that RSV reduced the infarct area and cerebral edema, prevented blood-brain barrier damage, improved neurological performance, and increased survival. Additionally, our findings suggest that the antioxidant activity of RSV targeted SP transcription factors and inhibited SUR1 and AQP4 expression. Thus, RSV by decreasing SUR1 expression could contribute to reducing edema formation, constituting a therapeutic alternative for edema reduction in stroke.

Resuscitating the Globally Ischemic Brain: TTM and Beyond

Cardiac arrest (CA) afflicts ~ 550,000 people each year in the USA. A small fraction of CA sufferers survive with a majority of these survivors emerging in a comatose state. Many CA survivors suffer devastating global brain injury with some remaining indefinitely in a comatose state. The pathogenesis of global brain injury secondary to CA is complex. Mechanisms of CA-induced brain injury include ischemia, hypoxia, cytotoxicity, inflammation, and ultimately, irreversible neuronal damage. Due to this complexity, it is critical for clinicians to have access as early as possible to quantitative metrics for diagnosing injury severity, accurately predicting outcome, and informing patient care. Current recommendations involve using multiple modalities including clinical exam, electrophysiology, brain imaging, and molecular biomarkers. This multi-faceted approach is designed to improve prognostication to avoid "self-fulfilling" prophecy and early withdrawal of life-sustaining treatments. Incorporation of emerging dynamic monitoring tools such as diffuse optical technologies may provide improved diagnosis and early prognostication to better inform treatment. Currently, targeted temperature management (TTM) is the leading treatment, with the number of patients needed to treat being ~ 6 in order to improve outcome for one patient. Future avenues of treatment, which may potentially be combined with TTM, include pharmacotherapy, perfusion/oxygenation targets, and pre/postconditioning. In this review, we provide a bench to bedside approach to delineate the pathophysiology, prognostication methods, current targeted therapies, and future directions of research surrounding hypoxic-ischemic brain injury (HIBI) secondary to CA.

Circulating miRNAs expression as potential biomarkers of mild traumatic brain injury

TBI is the main cause of death and disability in individuals aged 1-45 in Western countries. One of the main challenges of TBI at present is the lack of specific diagnostic biomarkers, especially for mild TBI (mTBI), which remains currently difficult to value in clinical practice. In this context MiRNAs may be important mediators of the profound molecular and cellular changes that occur after TBI in both the short and the long term. Recently, plasma miRNAs profiling in human TBI, have revealed dynamic temporal regulation of miRNA expression within the cortex. Aim of this study was to select a specific miRNAs panel for mTBI, by focusing the research on the prognostic meaning of miRNAs in the hours following the trauma, in order to be able to use this MIRNAs as potential biomarkers useful for monitoring the follow up of mild TBI. Serum levels of 17 miRNAs were measured by RT-quantitative polymerase chain reaction (qPCR) in 20 patients with mTBI at three different time-points (0 h, 24 h, 48 h) and in 10 controls. For 15 miRNAs we found a significant differences in the comparison among the three time points: for each of these miRNAs the values were greater at baseline and progressively reduced at 24 h and 48 h. These data allow us to consider the miRNAs included in panel as sensitive and specific biomarkers for mTBI, useful in monitoring the post-trauma period.

Blockade of the forward Na+ /Ca2+ exchanger suppresses the growth of glioblastoma cells through Ca2+ -mediated cell death

Background and Purpose

The Na⁺/Ca²⁺ exchanger (NCX) working in either forward or reverse mode participates in maintaining intracellular Ca²⁺ ([Ca²⁺]_i) homeostasis, which is essential for determining cell fate. Previously, numerous blockers targeting reverse or forward NCX have been developed and studied in ischaemic tissue injury but barely examined in glioblastoma for the purpose of anti‐tumour therapy. We assessed the effect of NCX blockers on glioblastoma growth and whether NCX can become a therapeutic target.

Experimental Approach

Patch‐clamp recording, Ca²⁺ imaging, flow cytometry, and Western blot were used to study the effects of specific and non‐specific NCX blockers on cultured glioblastoma cells. In vivo bioluminescent imaging was used to measure effects on grafted glioblastoma.

Key Results

Selectively blocking the reverse NCX with SEA0400, SN‐6, and YM‐244769 did not affect tumour cell viability. Blocking the forward NCX with bepridil, CB‐DMB, or KB‐R7943 elevated [Ca²⁺]_i and killed glioblastoma cells. Bepridil and CB‐DMB caused Ca²⁺‐dependent cell cycle arrest together with apoptosis, which were all attenuated by a Ca²⁺ chelator BAPTA‐AM. Systemic administration of bepridil inhibited growth of brain‐grafted glioblastoma. Bepridil did not appear to have a cytotoxic effect on human astrocytes, which have higher functional expression of NCX than glioblastoma cells.

Conclusions and Implications

Low expression of the NCX makes glioblastoma cells sensitive to disturbance of [Ca²⁺]_i. Interventions designed to block the forward NCX can cause Ca²⁺‐mediated injury to glioblastoma thus having therapeutic potential. Bepridil could be a lead compound for developing new anti‐tumour drugs.

Retinal Oxygen Delivery, Metabolism and Extraction Fraction and Retinal Thickness Immediately Following an Interval of Ophthalmic Vessel Occlusion in Rats

Limited knowledge is currently available about alterations of retinal blood flow (F), oxygen delivery (DO₂), oxygen metabolism (MO₂), oxygen extraction fraction (OEF), or thickness after the ophthalmic blood vessels have been closed for a substantial interval and then reopened. We ligated the ophthalmic vessels for 120 minutes in one eye of 17 rats, and measured these variables within 20 minutes after release of the ligature in the 10 rats which had immediate reflow. F, DO₂ and MO₂ were 5.2 ± 3.1 μL/min, 428 ± 271 nL O₂/min, and 234 ± 133 nL O₂/min, respectively, that is, to 58%, 46% and 60% of values obtained from normal fellow eyes (P < 0.004). OEF was 0.65 ± 0.23, 148% of normal (P = 0.03). Inner and total retinal thicknesses were 195 ± 24 and 293 ± 20 μm, respectively, 117% and 114% of normal, and inversely related to MO₂ (P ≤ 0.02). These results reflect how much energy is available to the retina immediately after an interval of nonperfusion for 120 minutes. Thus, they elucidate aspects of the pathophysiology of nonperfusion retinal injury and may improve therapy in patients with retinal artery or ophthalmic artery obstructions.

4-Imidazo[2,1-b]thiazole-1,4-DHPs and neuroprotection: preliminary study in hits searching

In the present work we describe the synthesis, characterization and evaluation of neuroprotective effects of a focused library of 4-imidazo[2,1-b]thiazole-1,4-dihydropyridines. Furthermore, the new dihydropyridines were subjected to functional in vitro assays in cardiac tissues and vascular smooth muscle to determine their possible selectivity in counteracting the effects of neurodegeneration. In particular the strategy adopted for designing the compounds involves the imidazo[2,1-b]thiazole nucleus. The observed properties show that substituents at C2 and C6 of the bicyclic scaffold are able to influence the cardiovascular parameters and the neuroprotective activity. In comparison to nifedipine, a set of derivatives such as compound 6, showed a neuroprotective profile of particular interest.

Glycine receptors are involved in hippocampal neuronal damage caused by oxygen-glucose deficiency

Glycine receptors (GlyRs) belong to the family of ligand-gated cys-loop receptors and effectuate fast inhibitory neurotransmission in central nervous system (CNS). They are involved in numerous physiological processes, such as movement, respiration, and processing of sensory information, as well as in regulation of neuronal excitability in different brain regions. GlyRs play important role in the maintenance of excitatory/inhibitory balance in the hippocampus and participate in the development of various brain pathologies. In the present study, we have examined a surface expression of GlyRs by pyramidal neurons and astrocytes in control and after 30 min of oxygen-glucose deprivation (OGD) in the organotypic culture of hippocampal slices. Our investigation has demonstrated a decrease in GlyR-positive staining associated with pyramidal neurons and relative stability of GlyRs expression at the surface of astrocytes 4 hs after OGD. These data indicate that GlyRs dysfunction may represent a significant additional factor leading to enhanced neuronal damage induced by OGD. Pharmacological modulation of GlyRs is a promising venue of research for the correction of negative consequences of oxygen-glucose deficiency.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO⁻), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.

Paradigm Shift to Neuroimmunomodulation for Translational Neuroprotection in Stroke

The treatment of acute ischemic stroke is still an unresolved clinical problem since the only approved therapeutic intervention relies on early blood flow restoration through pharmacological thrombolysis, mechanical thrombus removal, or a combination of both strategies. Due to their numerous complications and to the narrow time-window for the intervention, only a minority of stroke patients can actually benefit from revascularization procedures, highlighting the urgent need of identifying novel strategies to prevent the progression of an irreversible damage in the ischemic penumbra. During the past three decades, the attempts to target the pathways implicated in the ischemic cascade (e.g., excitotoxicity, calcium channels overactivation, reactive oxygen species (ROS) production) have failed in the clinical setting. Based on a better understanding of the pathobiological mechanisms and on a critical reappraisal of most failed trials, numerous findings from animal studies have demonstrated that targeting the immune system may represent a promising approach to achieve neuroprotection in stroke. In particular, given the dualistic role of distinct components of both the innate and adaptive arms of the immune system, a strategic intervention should be aimed at establishing the right equilibrium between inflammatory and reparative mechanisms, taking into consideration their spatio-temporal recruitment after the ischemic insult. Thus, the application of immunomodulatory drugs and their ability to ameliorate outcomes deserve validation in patients with acute ischemic stroke.

It's All about Timing: The Involvement of Kir4.1 Channel Regulation in Acute Ischemic Stroke Pathology

An acute ischemic stroke is characterized by the presence of a blood clot that limits blood flow to the brain resulting in subsequent neuronal loss. Acute stroke threatens neuronal survival, which relies heavily upon proper function of astrocytes. Neurons are more susceptible to cell death when an astrocyte is unable to carry out its normal functions in supporting the neuron in the area affected by the stroke (Rossi et al., 2007; Takano et al., 2009). For example, under normal conditions, astrocytes initially swell in response to changes in extracellular osmotic pressure and then reduce their regulatory volume in response to volume-activated potassium (K+) and chloride channels (Vella et al., 2015). This astroglial swelling may be overwhelmed, under ischemic conditions, due to the increased levels of glutamate and extracellular K+ (Lai et al., 2014; Vella et al., 2015). The increase in extracellular K+ contributes to neuronal damage and loss through the initiation of harmful secondary cascades (Nwaobi et al., 2016). Reducing the amount of extracellular K+ could, in theory, limit or prevent neuronal damage and loss resulting in an improved prognosis for individuals following ischemic stroke. Kir4.1, an inwardly rectifying K+ channel, has demonstrated an ability to regulate the rapid reuptake of this ion to return the cell to basal levels allowing it to fire again in rapid transmission (Sibille et al., 2015). Despite growing interest in this area, the underlying mechanism suggesting that neuroprotection could occur through modification of the Kir4.1 channel's activity has yet to be described. The purpose of this review is to examine the current literature and propose potential underlying mechanisms involving Kir4.1, specially the mammalian target of rapamycin (mTOR) and/or autophagic pathways, in the pathogenesis of ischemic stroke. The hope is that this review will instigate further investigation of Kir4.1 as a modulator of stroke pathology.

Oncotic Cell Death in Stroke

Oncotic cell death or oncosis represents a major mechanism of cell death in ischaemic stroke, occurring in many central nervous system (CNS) cell types including neurons, glia and vascular endothelial cells. In stroke, energy depletion causes ionic pump failure and disrupts ionic homeostasis. Imbalance between the influx of Na⁺ and Cl^- ions and the efflux of K⁺ ions through various channel proteins and transporters creates a transmembrane osmotic gradient, with ensuing movement of water into the cells, resulting in cell swelling and oncosis. Oncosis is a key mediator of cerebral oedema in ischaemic stroke, contributing directly through cytotoxic oedema, and indirectly through vasogenic oedema by causing vascular endothelial cell death and disruption of the blood-brain barrier (BBB). Hence, inhibition of uncontrolled ionic flux represents a novel and powerful strategy in achieving neuroprotection in stroke. In this review, we provide an overview of oncotic cell death in the pathology of stroke. Importantly, we summarised the therapeutically significant pathways of water, Na⁺, Cl^- and K⁺ movement across cell membranes in the CNS and their respective roles in the pathobiology of stroke.